The present disclosure relates to image processing apparatuses and methods, and programs, and more specifically to an image processing apparatus and method, and a program that can quickly apply an effect of artistic style such as painting to an image.
Techniques are available for converting an input image to obtain an output image having a painting style. Such techniques are called non photo-realistic rendering (NPR) techniques. One of the NPR techniques is a technique for repeatedly adding a pattern resembling brush strokes to an image to obtain an image similar to that rendered in the style of an oil painting.
For example, Japanese Unexamined Patent Application Publication No. 8-44867 (corresponding U.S. Pat. No. 5,621,868) (hereinafter referred to the “patent literature”) proposes an algorithm in which a process for replacing each pixel in a certain elliptical region with the value of the pixel at the center thereof is performed on an input image to generate a pattern resembling a brush stroke and to obtain an output image similar to an image rendered in the style of an oil painting.
In addition, A. Hertzmann has proposed, in “Painterly Rendering with Curved Brush Strokes of Multiple Sizes,” Proc. Sgigraph 98, ACM Press, 1998, pp. 453-460 (hereinafter referred to as the “non-patent literature”), an algorithm in which an image buffer is repeatedly rendered over with brush stroke patterns to obtain output images and the squared error between the input image and each of the output images is reduced to obtain a resulting image similar to an image rendered in an oil painting style. In this technique, rendering with different shapes of brush stroke patterns makes it possible to provide various painting styles of output images. For example, rendering with a circular brush stroke pattern allows an output image similar to an image rendered in a pointillist style, and using curved brush strokes provides an output image similar to an image rendered in an impressionist style.